Insects and other arthropods constitute over half of the living animal species on earth; they are important not only from a biological viewpoint, but also as disease vectors and as agricultural, forest, and household pests. Insects interact chemically with one another, with plants, with animal hosts, and with predators. This project is concerned with elucidating these chemical interactions, which can influence both behavior and development. Among the arthropods to be studied are millipeds, centipedes, opilionids, beetles, ants, and lepidoptera. Some specific objectives include the study of (1) the structures, synthesis, and biological origins of the lucibufagins, cardiotonic steroids which we recently discovered in fireflies, (2) repellents, feeding deterrents and toxins from a wide variety of arthropods, and (3) pheromones of lepidoptera which may elucidate new insect-plant dependencies, and the importance of pulsed signals in chemical communication. We plan to carry out syntheses of any new compounds, when these would be important, and to screen appropriate new compounds for cardiotonic, antibiotic, and antitumor activities. Our overall objectives are (1) to increase our understanding of natural regulatory mechanisms so as to provide the basis for new control techniques of disease vectors and other pests, and (2) to discover new natural products which may be useful in combatting disease.